1. Field of the Invention
The present invention relates to a wheel cap which is capable of preventing rise in temperatures of a brake pad, a disc wheel, a wheel cap and so forth.
The present application is based on Japanese Patent Applications No. Hei. 10-194085 and 10-198853, which are incorporated herein by reference.
2. Description of the Related Art
A conventional wheel cap having air discharge openings 99 formed in the outer periphery thereof is shown in FIG. 20.
After the wheel cap 9 has been joined to the disc wheel 2, outside air is allowed to flow from the inside portion of the disc wheel 2 to the air discharge openings 99. Thus, rise in the temperature of a brake pad caused from the operation of a brake unit is prevented so that wear of the brake pad 31 is reduced.
However, the conventional wheel cap 9 has the following problems.
As shown in FIG. 20, the wheel cap 9 is not provided with any openings in a region between the hub nut 21 and the center of wheel cap 9.
That is, the air discharge openings 99 are formed further out than the hub nut 21 of the disc wheel 2.
Therefore, airflow 4 occurring after the wheel cap 9 has been joined to the disc wheel 2 do not substantially pass through the hub nut 21.
That is, when the wheel cap 9 has been joined as described above, air 4 is sucked from the inside portion of the disc wheel 2 as indicated with an arrow shown in FIG. 20. Then, air 4 is allowed to pass through holes 22 provided for the disc wheel 2, and then discharged to the outside through the air discharge openings 99 formed in the periphery of the wheel cap 9.
As described above, a major portion of air 4 is allowed to pass through the outer portion of a brake disc 32, the disc wheel 2 and the wheel cap 9. That is, air 4 is not allowed to pass through the central portion including the hub nut 21 and the axle hub 33 when air 4 is discharged to the outside.
Therefore, the central portion of each of the brake disc 32, the disc wheel 2 and the axle hub 33 is not sufficiently cooled down. Also the hub nut 21 is not cooled down sufficiently.
As a result, the temperatures of the central portions of the brake disc 32, the axle hub 33 and the disc wheel 2 are raised. Further, an interior space 5 between the wheel cap 9 and the disc wheel 2 is narrow and no forcible air discharge means is provided therein, as shown in FIG. 20. Therefore, even if a small amount of air 4 is introduced into the interior space 5, circulation of air 4 sucked into the interior space 5 through the through holes 22 cannot smoothly be performed. Thus, stagnation of air 4 easily occurs in the interior space 5.
Therefore, the axle hub 33, the hub nut 21, the disc wheel 2, the wheel cap 9 and so forth cannot sufficiently be cooled down. Therefore, there is a possibility that the rise in the temperatures cannot be prevented.
The rise in the temperature of the disc wheel 2 is caused from conduction of heat of the brake disc 32 through the axle hub 33 and the hub nut 21.
Therefore, the rise in the temperature of the hub nut 21 causes the temperatures of the disc wheel 2 and the wheel cap 9 joined to the disc wheel 2 to be raised. As a result, there is a possibility that the brake pad is quickly worn and the wheel cap is deformed.
If the hub nut 21 is not cooled down sufficiently, the rise in the temperatures of the disc wheel 2 and the wheel cap 9 cannot easily be prevented.
In view of the foregoing, an object of the present invention is to provide a wheel cap which is capable of preventing rise in the temperatures of the disc wheel, the wheel cap and so forth after the wheel cap has been joined to the disc wheel.
According to one aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel and having air discharge openings formed in the outer periphery thereof, the wheel cap comprising: a plurality of radial fins provided for the reverse side of the wheel cap and formed from the wheel cap center toward the outside.
An essential portion of the present invention is the structure that the plural radial fins are provided for the reverse side of the wheel cap and formed from the wheel cap center toward the outside.
The operation and effect of the present invention will now be described.
As described above, the plural fins are provided for the reverse side of the wheel cap. As a result, centrifugal force is imparted to air sucked into the interior space between the wheel cap and the disc wheel owning to rotations of the wheel. Thus, air is sent to the air discharge openings formed at the outer periphery of the wheel cap along the fins.
That is, the centrifugal force is generated when air is rotated as a result of rotations of the wheel. Since the fins are provided for the reverse side of the wheel cap as described above, air can efficiently be rotated. Thus, great centrifugal force is imparted to air.
As a result, air in the interior space can efficiently be sent to the air discharge openings.
Therefore, the quantity of air which is circulated in the interior space can be enlarged. As a result, the efficiency of cooling the disc wheel and so forth can be improved.
As described above, according to the present invention, a wheel cap can be obtained which is able to prevent a rise in the temperatures of the disc wheel, the wheel cap and so forth after the wheel cap has been joined to the disc wheel.
It is preferable that the plural fins are formed from the wheel cap center to the outer end of the wheel cap.
As a result, air existing from the wheel cap center to the outer periphery of the wheel cap can be rotated when the wheel has been rotated. Therefore, greater centrifugal force can be imparted.
Therefore, the quantity of air which is circulated in the interior space can furthermore be enlarged. Thus, the efficiency of cooling the disc wheel can furthermore be improved.
It is preferable that when an assumption is made that the radius of the wheel cap is R, the plural fins are formed on straight lines, which connect the wheel cap center and the outer end of the wheel cap to each other, in regions from about R/2 from the wheel cap center to the outer end of the wheel cap. As a result, the quantity of air which is circulated in the interior space can be increased(refer to experiment 1). Moreover, a wheel cap having a reduced weight can be obtained.
It is preferable that when an assumption is made that the radius of the wheel cap is R, the plural fins are formed on straight lines which connect the wheel cap center and the outer end of the wheel cap to each other, in regions from positions of distance 3R/4 from the wheel cap center to the outer end of the wheel cap.
As a result, the quantity of air which is circulated in the interior space can be increased(refer to experiment 1). Moreover, a wheel cap having an even more reduced weight can be obtained.
It is preferable that when an assumption is made that the radius of the wheel cap is R, the plural fins are formed on straight lines which connect the wheel cap center and the outer end of the wheel cap to each other in regions from positions about R/2 from the wheel cap center to positions about 3R/4.
As a result, a wheel cap having a small weight can be obtained.
It is preferable that the number of the fins provided for the wheel cap is 20 to 30.
As a result, air in the interior space between the wheel cap and the disc wheel can be efficiently rotated. Therefore, the quantity of air which is circulated in the interior space can be increased (refer to experiment 2).
If the number of the fins is smaller than 20, the effects of the fins may not sufficiently increase the quantity of air which is circulated in the interior space. If the number of the fins is larger than 30, the effect required to improve the air circulation by enlarging the number of the fins becomes unsatisfactory. Thus, there arises a problem in that the weight of the wheel cap is enlarged.
Therefore, according to the present invention, a wheel cap exhibiting an excellent efficiency of cooling the disc wheel can be obtained.
It is preferable that when the radius of the wheel cap is R, the plural fins are formed along the radius except for a portion adjacent to the wheel cap center in which the distance from the wheel cap center is R/20 to R/10 and an outer portion in which the distance from the wheel cap center is 9R/10 to 19R/20 (see FIG. 3).
As a result, a wheel cap can be obtained which is capable of increasing the quantity of air which is circulated in the interior space, which can easily be manufactured and which can easily be joined to the disc wheel can be obtained.
It is preferable that the wheel cap has an annular air suction opening and a center plate disposed closer to the center of the wheel cap than the air suction opening, and inner distance C between the innermost wall of the air suction opening and the wheel cap center is shorter than securing distance D between a securing position at which the disc wheel is secured to an axle hub and the disc wheel center (see FIG. 2)
After the wheel cap has been joined to the disc wheel, the air suction opening is positioned closer to the disc wheel center than the securing position. Therefore, air is introduced into the interior space from the position closer to the disc wheel center than with the securing position, and then discharged through the air discharge openings (see FIG. 2).
Therefore, air is allowed to pass through the centers of the hub nut at the securing position, the brake disc, the axle hub and the disc wheel. Thus, the foregoing elements can sufficiently be cooled down.
As a result, a rise in the temperatures of the central portions of the brake disc, the axle hub and the disc wheel can be prevented.
Since the hub nut and so forth can sufficiently be cooled down, conduction of heat from the brake disc and the axle hub to the disc wheel can be prevented. As a result, rise in the temperatures of the disc wheel and the wheel cap joined to the disc wheel can be prevented.
According to another aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel and having air discharge openings formed in the outer periphery thereof, the wheel cap comprising: an annular air suction opening; and a center plate disposed more adjacent to the center thereof as compared with the air suction opening, wherein inner distance A between the innermost wall of the air suction opening and the center of the wheel cap is shorter than the securing distance D between a securing position at which the disc wheel is secured to an axle hub and the center of the disc wheel.
An essential portion of the present invention is a structure in which the inner distance A between the innermost wall of the air suction opening and the center of the wheel cap is shorter than securing distance D between a securing position at which the disc wheel is secured to an axle hub and the center of the disc wheel (see FIG. 9).
The operation and effect of the foregoing aspect will now be described.
After the wheel cap has been joined to the disc wheel, the air suction opening is formed at a position closer to the center of the disc wheel than the securing position. Therefore, air is introduced into a space between the disc wheel and the wheel cap through a position closer to the center of the disc wheel than the securing position. Then, air is discharged through the air discharge openings (as indicated with an arrow shown in FIG. 7).
Therefore, air is allowed to pass through the securing position, the center portions of the brake disc, the axle hub and the disc wheel.
As a result, the center portions of the brake disc, the axle hub and the disc wheel and the hub nut secured to the securing position can sufficiently be cooled down.
Moreover, a rise in the temperatures of the center portions of the brake disc, axle hub and the disc wheel can be prevented.
Since the hub nuts and so forth can sufficiently be cooled down, heat conduction from the brake disc and the axle hub to the disc wheel can be prevented. As a result, rise in the temperature of the disc wheel and the wheel cap joined to the disc wheel can be prevented.
As a result, according to the present invention, a wheel cap can be obtained which is able to prevent rise in the temperatures of the brake pad, the disc wheel and the wheel cap after the wheel cap has been joined to the disc wheel.
It is preferable that a distance B between the outermost wall of the air suction opening and the center of the wheel cap is shorter than the securing distance D (see FIG. 9).
As a result, air sucked through the air suction opening is efficiently allowed to pass through the hub nut and so forth. Thus, the hub nut and so forth can efficiently be cooled down.
After the wheel cap has been joined to the disc wheel, the hub nut and so forth cannot be seen. Thus, the quality of the design can be improved.
It is preferable that the center plate is disposed to retract to the reverse side of the wheel cap.
Note that the xe2x80x9creverse sidexe2x80x9d is a side on which the wheel cap is joined to the disc wheel.
As a result, the quantity of air which is sucked through the air suction opening can be enlarged so that the efficiency of cooling the disc wheel and so forth is furthermore improved.
It is preferable that the center plate projects over the right side of the wheel cap.
Note that the xe2x80x9cright sidexe2x80x9d is the side opposite to the foregoing reverse side.
The efficiency of cooling the disc wheel and so forth can furthermore be improved.
It is preferable that the reverse side of the wheel cap has a plurality of fins formed radially from the center of the reverse side of the wheel cap toward the outside.
As a result, centrifugal force generated because of rotations of the wheel is imparted to air sucked through the air suction opening. As a result, air is moved to the air discharge openings formed in the outer periphery of the wheel cap, along the fins.
That is, the centrifugal force is generated when air is rotated owning to rotations of the wheel. When the fins are provided for the reverse side of the wheel cap as described above, air can efficiently be rotated. As a result, greater centrifugal force is imparted to air.
Therefore, air can efficiently be moved to the air discharge opening.
As a result, an amount of air which is circulated in the wheel cap can be increased so that the efficiency of cooling the disc wheel and so forth is furthermore improved.
According to yet another aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel, comprising: air discharge openings formed in the outer periphery thereof, wherein the air discharge openings of the wheel cap are openings opened toward outside.
That is, each air discharge opening is formed in a cut-out shape. After the wheel cap has been joined to the disc wheel, a gap is formed between each air discharge opening in the form of the cut-out shape and the end of the disc wheel.
The operation and effect of the present invention will now be described.
The wheel cap has air discharge openings in the outermost portion thereof. Therefore, air sucked into the space between the wheel cap and the disc wheel is discharged through the outermost portion of the wheel cap.
Therefore, an excellent air discharge characteristic can be produced. Moreover, the overall body of the disc wheel and so forth can be cooled down efficiently.
Each air discharge opening is formed into the cut-out shape formed in the outer end of the wheel cap, that is, the air discharge opening is not formed into a through hole. Therefore, portions of resin for molding are not in contact with each other in the outer portion when the wheel cap is molded.
Therefore, formation of stripes can be prevented as often occurs in the outer portion of the conventional wheel cap. As a result, the quality of the appearance does not deteriorate.
Since the wheel cap has the outer end in the form of the cut-out shape, a gap is formed from the end of the disc wheel in a state in which the wheel cap has been joined to the disc wheel.
Therefore, the wheel cap can be easily removed from the disc wheel by inserting a tool or the like into the gap.
Each of the air discharge openings is formed into the cut-out shape facing the outside. Therefore, when dust or the like of the brake pad is, together with air, discharged through the air discharge openings, it does not adhere to the designed surface of the wheel cap.
Therefore, a wheel cap can be obtained which cannot easily be contaminated.
The foregoing wheel cap is not required to have an opening which is formed on the designed surface thereof. Therefore, the designed surface can be flattened. As a result, the operation for cleaning the wheel cap can easily be performed. Moreover, a satisfactory cd value can be obtained.
As described above, according to the present invention, a wheel cap can be obtained which is capable of preventing rise in the temperatures of the brake pad, the disc wheel and the wheel cap and which exhibits an excellent design quality.
According to still another aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel, comprising: air discharge openings formed in the outer periphery thereof, wherein discharge opening distance C between the innermost wall of each air discharge opening and the center of the wheel cap is longer than through-hole distance K between the outermost wall of each through hole provided for the disc wheel and the center of the disc wheel.
The operation and effect of the foregoing aspect will now be described.
After the wheel cap has been joined to the disc wheel, the air discharge openings are brought to the positions further out than the through holes of the disc wheel (see FIG. 7).
Air allowed to pass through the through holes from the inside portion of the disc wheel is discharged through the air discharge openings of the wheel cap. Since the air discharge openings are positioned further out than the through holes, centrifugal force generated as a result of rotations of the wheel and acting in the direction toward the air discharge openings is imparted to air allowed to pass through the through holes.
Therefore, the amount of air which is circulated in the wheel cap can be increased and, thus, the efficiency of cooling the disc wheel and so forth can be improved.
As described above, a wheel cap can be obtained which is able to efficiently cool the disc wheel and so forth after the wheel cap has been joined to the disc wheel.
According to still another aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel, comprising: air discharge openings formed in the outer periphery thereof, wherein the air discharge openings are formed on straight lines connecting the through holes provided for the disc wheel and the center of the disc wheel to one another.
The operation and effect of the present invention will now be described.
After the foregoing wheel cap has been joined to the disc wheel, air allowed to pass through the through holes from the inside portion of the disc wheel is discharged through the air discharge openings of the wheel cap. The air discharge openings are formed on the straight lines connecting the through holes and the center of the disc wheel to one another (as indicated with reference numerals 19 and 19A shown in FIG. 14). Therefore, air allowed to pass through the through holes can smoothly be discharged through the air discharge openings.
As a result, the amount of air which is circulated in the wheel cap can be enlarged. As a result, the efficiency of cooling the disc wheel and so forth can be improved.
As described above, according to the present invention, a wheel cap can be obtained which is capable of efficiently cooling the disc wheel and so forth after the wheel cap has been joined to the disc wheel.
According to still another aspect of the present invention, there is provided a wheel cap detachably joined to a disc wheel, comprising: air discharge openings formed in the outer periphery thereof, wherein the air discharge openings of the wheel cap do not incorporate a discharge opening fin projecting toward the reverse side of the wheel cap at least in the central portion of the wheel cap.
Note that the xe2x80x9cdischarge opening finxe2x80x9d is a projecting plate projecting over the reverse side of the wheel cap to surround the air discharge openings.
The operation and effect of the present invention will now be described.
After the wheel cap has been joined to the disc wheel, flows of air in the wheel cap are directed from the center of the disc wheel to the outside as a result of centrifugal force provided by the rotation of the disc wheel. Since no discharge opening fin is provided for the air discharge opening adjacent to the center of the wheel cap, the air flow is not obstructed. Therefore, air can be allowed to flow smoothly to the air discharge openings so as to be discharged to the outside.
Therefore, the amount of air which is circulated in the wheel cap can be enlarged so that the efficiency of cooling the disc wheel and so forth is improved.
As described above, according to the present invention, a wheel cap can be obtained which is able to efficiently cool the disc wheel and so forth after the wheel cap has been joined to the disc wheel.
It is preferable that the wheel cap has an annular air suction opening and a center plate disposed closer to the center thereof than the air suction opening, wherein inner distance A between the innermost wall of the air suction opening and the center of the wheel cap is shorter than the securing distance D between a securing position at which the disc wheel is secured to an axle hub and the center of the disc wheel.
As a result, thanks to similar operation and effect of the aspect of the present invention, rise in the temperatures of the brake pad, the disc wheel and the wheel cap can furthermore efficiently be prevented after the wheel cap has been joined to the disc wheel.
It is preferable that distance B between the outermost wall of the air suction opening and the center of the wheel cap is shorter than the securing distance D (see FIG. 9).
As a result, air sucked through the air suction opening is, similarly to the aspect of the present invention, efficiently allowed to pass through the hub nut and so forth. Thus, the hub nut and so forth can efficiently be cooled down.
Since the hub nut and so forth cannot be observed from outside after the wheel cap has been joined to the disc wheel, the design quality can be improved.
It is preferable that in one embodiment of the present invention the center plate is disposed to retract to the reverse side of the wheel cap.
As a result, the quantity of air which is sucked through the air suction opening can be enlarged. As a result, the efficiency of cooling the disc wheel and so forth can furthermore be improved.
It is preferable that the center plate projects over the right side of the wheel cap.
Also in the foregoing case, the efficiency of cooling the disc wheel and so forth can furthermore be improved.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with attached drawings.